Members of this family, which are uniquely found in bacterial and archaeal glucoamylases and glucodextranases, adopt a structure consisting of 17 antiparallel beta-strands. These beta-strands are divided into two beta-sheets, and one of the beta-sheets is wrapped by an extended polypeptide, which appears to stabilise the domain. Members of this family are mainly concerned with catalytic activity, hydrolysing alpha-1,6-glucosidic linkages of dextran to release beta-D-glucose from the non-reducing end via an inverting reaction mechanism [1].

1: Structural insights into substrate specificity and function of glucodextranase. Mizuno M, Tonozuka T, Suzuki S, Uotsu-Tomita R, Kamitori S, Nishikawa A, Sakano Y; J Biol Chem. 2004;279:10575-10583. PMID:14660574